1. Field of the Invention
The present invention relates generally to engine controls, and more particularly to an engine torque control algorithm to reduce undesirable accelerations and oscillations from the powertrain during a closed throttle to open throttle transition.
2. Background and Summary of the Invention
Vehicles equipped with manual transmissions will develop a rapid undesirable acceleration (known as jerk) and oscillations (known as bobble) from the powertrain during the closed throttle to open throttle transition. Typically, what happens when the accelerator pedal is released during low speed operation such as city driving, and is then subsequently reapplied, the engine produces a sudden increase in torque which causes some of the powertrain components such as the drive shaft to twist (somewhat like a torsion spring), as the components of a powertrain become spring loaded, the release of the spring tension creates the undesirable accelerations and oscillations which are most prominently experienced during low speed operation of a vehicle having a manual transmission.
The present invention provides a torque algorithm to control the rate at which torque is produced from the engine. On manual transmission vehicles equipped with mechanical throttle bodies, spark advance/retard has the greatest effect on controlling the torque rate. The control system of the present invention controls spark advance/retard in order to control the torque rate.
The present invention provides a torque control algorithm for reducing jerk and bobble for an automotive vehicle powertrain including means for determining a proportional error term by monitoring an amount of torque the engine will produce and is presently producing during a closed to open throttle transition. Means are provided for determining a derivative error term by monitoring a rate of change of the engine speed during a closed to open throttle transition. Means are provided for determining a torque error term as the greater of the proportional error term and the derivative error term. Means are further provided for converting the torque error term to a spark compensation amount and for delivering the spark compensation amount to an engine control scheme. The proportional error term is determined based upon a sum of a potential torque term and a desired torque term minus an actual torque term. The derivative error term is determined based upon a derivative of engine acceleration over time since open throttle. The derivative error term is compared to be within a control window, and if not, is converted to a torque error value.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood however that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.